1. Field of the Invention.
This invention relates in general to a communication systems, and more particularly to a method and apparatus for providing mini packet switching in IP based networks, such as IP based cellular access networks and IP telephony (IPTEL) gateway networks.
2. Description of Related Art.
An Internet is a set of networks connected by gateways, which are sometimes referred to as routers. The Internet Protocol (IP) is a network layer protocol that routes data across an Internet. The Internet Protocol was designed to accommodate the use of host and routers built by different vendors, encompass a growing variety of growing network types, enable the network to grow without interrupting servers, and support higher-layer of session and message-oriented services. The IP network layer allows integration of Local Area Network xe2x80x9cislandsxe2x80x9d.
The Internet not only provides a medium for data transport, but also has developed as a medium for telecommunications. In fact, IP telephony is maturing as a technology and a service, which places it in direct conflict with the conventional public telephone network. New types of IP telephony equipment are being introduced and small Internet service providers and niche carriers are beginning to offer IP telephony services.
There are some very clear trends emerging in the communications world. For example, there is a clear trend in the increase in mobile penetration, the rise in Internet usage, and a growing interest in voice over the Internet and VoIP services. Accordingly, it comes as no surprise that the cellular industry is working on services offerings that take advantage of these trends. However, substantial investment is required and methods for upgrading mobile networks to cope with increasing IP traffic must be developed. Nevertheless, the growth in packet data traffic looks to continue, thereby making IP hard to disregard.
The technologies for upgrading mobile networks are here, or at least very nearly. For example, with respect to GSM, the packet upgrade is GPRS (global packet radio services), and in CDMA, Phase B Data services promise to bring packet functionality. Meanwhile wireless access protocol (WAP) promises to provide the important middleware element.
Anticipating this growth, many cellular equipment manufacturers are seriously considering an IP based transport technology in the cellular access and core networks. Mobile telephony is currently the dominant application in a cellular network and it is expected to remain so for many more years. Due to the resource limitation in the air interface, speech compression methods are implemented in the mobile terminal. The average packet size of current speech coders is in the range of 10 bytes. When such a small packet is transported using IP or ATM layers, a huge overhead is incurred due to transport layer headers. When the compressed speech packets arrive at the Base Station (BS), it is transported in the radio access network either to the Radio Network Controller (RNC) or to the Mobile Switching Center (MSC) based on the destination address. ATM Adaptation layer 2 (AAL2), a multiplexing scheme at the ATM cell level, has been standardized by the International Telecommunications Union-Telecommunications Standardization Sector (ITU-T) to carry compressed speech in an ATM environment. The main problem in transporting the small packets in a regular RTP based IP telephony model is the large amount of overhead due to RTP/UDP/IP headers.
A telephone call between users is typically carried by a separate Real-time Transport Protocol/User Datagram Protocol/Internet Protocol (RTP/UDP/IP) connection. RTP is an Internet protocol for transmitting real-time data such as audio and video. RTP itself does not guarantee real-time delivery of data, but it does provide mechanisms for the sending and receiving applications to support streaming data. Typically, RTP runs on top of the UDP protocol, although the specification is general enough to support other transport protocols. The User Datagram Protocol is a connectionless protocol that, like TCP, runs on top of IP networks. Unlike TCP/IP, UDP/IP provides very few error recovery services, offering instead a direct way to send and receive datagrams over an IP network.
IP telephony gateways provide an interface between the existing circuit switched telephone networks (such as PSTN and GSM) and the packet switched IP data networks. In traditional IP telephony applications, telephone calls between PSTN users interconnected by a pair of IP telephony gateways to compress incoming PSTN speech samples generate packets with sizes ranging from 5 to 20 bytes per speech sample.
For example, G.723.1 (the most popular IP telephony codec and the International Multimedia Teleconferencing Consortium""s (IMTC) Voice over IP (VoIP) mandatory low bit-rate codec), generates a 20 byte speech packet at 30 ms intervals. Many codecs used in cellular environment generate less than 10 byte packet per speech sample. Small size packets are subjected to large overhead when transferred using the Real time Transport Protocol (RTP). The RTP/UDP/IP overhead is 40 bytes (12+8+20) for a simple speech packet. For example, a 10 byte packet transferred via RTP/UDP/IP increases the overhead to 80% (40 byte overhead/50 byte overhead plus packet). In addition, for each call request a single UDP/IP connection (a pair of UDP ports) is established between the gateways requiring a large state (memory) to be maintained at the telephony gateways, thereby making these less scaleable.
Co-pending and commonly assigned U.S. Pat. application Ser. No. 09/137,276, filed on Aug. 20, 1998, by Baranitharan Subbiah, entitled METHOD AND APPARATUS FOR PROVIDING EFFICIENT USER MULTIPLEXING IN A REAL-TIME PROTOCOL PAYLOAD FOR TRANSPORTING COMPRESSED SPEECH BETWEEN IP TELEPHONY GATEWAYS, which is hereby incorporated by reference, discloses an efficient real-time transport protocol multiplexing method and apparatus for transporting compressed speech between IP telephony gateways. Subbiah includes creating a header for a plurality of data packets, wherein each header provides identification of a user associated with a packet. Then, each header is added to the data packet associated therewith to form mini-IP payloads. The mini-IP payloads are multiplexed into a RTP payload and the RTP payload is transmitted over a single RTP/UDP/IP connection. Thus, Subbiah multiplexes a number of users in to a single RTP/UDP connection. However, Subbiah is applicable only between a pair of nodes.
An IP based Radio Access Network (RAN) or Core Network (CN) requires that the solution proposed by Subbiah be extended so that it can be used for switching the mini packets. For example, a RAN consists of many BSs and RNCs. At any given time, there are several calls between any two network elements in the RAN and these calls are transferred via one or more intermediate network elements.
It can be seen then that there is a need for a new method which will allow mini packets belonging to several users that are received on incoming links to be multiplexed prior to sending it out on an outgoing link to maximize the efficiency of links between any two network elements.
It can also be seen that there is a need for a signaling scheme that establishes a connection between the source and destination node, wherein channels at each intermediate node are associated for a single end-to-end connection.
It can also be seen that there is a need for a method that enables demultiplexing and multiplexing mini packets at intermediate nodes in a RAN and CN.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for providing mini packet switching in IP access networks, such as IP based cellular access networks and IP telephony (IPTEL) gateway networks.
The present invention solves the above-described problems by providing a signaling scheme that establishes a connection between the source and destination node, wherein channels at each intermediate node are associated for a single end-to-end connection. This enables demultiplexing and multiplexing mini packets at intermediate nodes in a RAN and CN.
A method in accordance with the principles of the present invention includes receiving a payload at a node, the payload including a plurality of multiplexed mini packets, each mini packet having a header, wherein the header identifies a user and a connection associated therewith, demultiplexing the mini packets, analyzing the header of each mini packet to determine a processing for the mini packet and multiplexing packets having a common next hop in a new RTP payload.
Other embodiments of a method in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the analyzing further comprises identifying mini packets destined for a local user, the method further comprising transferring the mini packet to the local user.
Another aspect of the present invention is that the method further includes transmitting the new payload to the common next hop.
Another aspect of the present invention is that the analyzing the header of each mini packet to determine a processing for the mini packet further comprises updating a local channel identification table.
Another aspect of the present invention is that the updating the local channel identification table comprises updating only incoming parameters when the payload is received by a non-intermediate node.
Another aspect of the present invention is that the updating the local channel identification table comprises updating an incoming port parameter, an incoming channel identification parameter, an outgoing port parameter, an outgoing channel identification parameters, a calling user identification parameter and a called user identification parameter when the payload is received by an intermediate node.
Another aspect of the present invention is that the node is a base station.
Another aspect of the present invention is that the node is a radio network controller.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.